The present invention relates to mass information storage media and more particularly to a mass storage medium that in addition to being serially accessible is quasi-randomly accessible.
Optical tape mass information storage systems are known, for example as described in U.S. Pat. Nos. 3,262,122 and 4,199,783, incorporated herein by reference. Optical tape enjoys the same high storage density as the more popular compact disc, but because of the vastly greater surface area of a typical optical tape, it has a much greater overall storage capacity than a compact disc. Unfortunately, this advantage has often been more than offset by the disadvantage that optical tape has been only serially accessible. Absent some knowledge a priori of how and in what order information will be retrieved from the optical tape that may be taken into account in arranging information on the tape, a typical access requires an average of half the length of the tape to be wound from one reel to another in order to retrieve a given piece of information. Such an operation may take minutes, effectively preventing optical tape from finding widespread application in the real-time interactive computer environment. If the average access time of optical tape could be reduced from on the order of minutes to on the order of seconds, a myriad of applications in archival information storage and super-massive databases would be opened up.